1. Field of the Invention
The present invention relates to an energy detection apparatus and an energy detection method. More particularly, the present invention relates to an energy detection apparatus and an energy detection method that operates with no time delay.
2. Description of the Related Art
Digital signals play an important role in the processing of multimedia data. One of the applications of digital signals is in the transmission of one-dimensional digital sound information. The integration of audio and digital signal processing is indispensable for telecommunication.
In audio data signaling, a large quantity of data is continuously transmitted and it may include considerably incorrect noise signals and interferences. To capture correct signals, the signals must be checked to determine if they are correct or not. Conventionally, the process of determining whether a signal should be captured includes detecting the strength of the signal energy. Briefly, when the energy level detected at a definite time point is higher than a preset energy threshold, the signal at the next time point can be captured and used. On the contrary, if the energy level is lower than the threshold value, the signal at the next time point is regarded as a noise signal so that capturing is stopped. Typically, the energy detection involves sampling the initial input signal to obtain an input analogue signal. After the processes of dispersing and converting the analogue signal into digital signal, a number of samples are used for finding an average energy value for a definite time interval. This average energy value is served as the basis for recognizing the energy level for the energy detection. In the following, the conventional energy detection method is briefly discussed.
FIGS. 1A, 1B and 1C schematically show an input signal sampling diagram, an output waveform diagram of energy detection result, and an output diagram of the signaling sample captured and processed according to the energy detection result. FIG. 1A is an input signal sampling diagram. As shown in FIG. 1A, a number of input signals is sampled in sequence and converted into absolute values. In a common energy detection method, to be effective in estimating, computing and detecting the energy values, a detection window is often defined. The detection window serves as a standard in the computation for determining the energy values, that is, defining the length of sampling period and the number of samples as a base for energy detection. For example, as shown in FIG. 1A, the detection window has a time length of 8 samples. In FIG. 1A, the sampling for the nth time block and the (n+1)th time block according to the aforementioned detection window size is sketched.
FIG. 1B shows the output waveform of the energy detection result. To carry out the energy detection, the sampled input signal data for a time block is registered and stored in a memory. After using the data to compute the energy values, whether to process or capture and output the sampled data stored in the memory is determined according to the computed energy values. FIG. 1C shows the output diagram of capturing the signal samples according to the energy detection result. From FIGS. 1A through 1C, it can be easily seen that the sampling operation is still progressing sequentially during the nth time block (see the nth time block in FIG. 1A). However, the output of the energy detection result and the sample output according to the energy detection result are the values obtained in the (n−1)th time block. In other words, the energy detection in any time block is based on the values obtained from the previous time block stored in the memory. It means the current energy detection has to depend on the previously collected samples. Since there is a time delay in the energy detection, a real-time detection of the energy values is impossible and cost of memories for registering and storing data is required. Thus, the major defects of this type of energy detection method are time delay in energy detection and additional cost of memories.
FIGS. 2A, 2B and 2C schematically show an input signal sampling diagram, an output waveform diagram of energy detection result and an output diagram of the signaling samples captured and processed according to the energy detection result, for another method of energy detection in the prior art. FIG. 2A is an input signal sampling diagram similar to the one in FIG. 1A. As shown in FIG. 2A, a number of input signals is sampled in sequence and converted into absolute values.
FIG. 2B shows the output waveform of the energy detection result. The method is slightly different from the previous one because the input signal sampled data is not stored in the memory. Instead, a hardware having a capability similar to a digital signal-processing program is used to perform the accumulation and computation for obtaining the energy value of the previous time block. According to the obtained energy value, whether to process or capture the currently sampled data is determined. As shown in FIGS. 2A through 2C, although the hardware can immediately output the values obtained from the sampled data, that is, it can immediately output the value after the value of the nth time block has been input (the output diagram in FIG. 1C), the energy detection result of the (n−1)th time block is still used. Therefore, there is still a time delay between the energy detection result and the sampled data output in this energy detection method.
Accordingly, the conventional energy detection methods not only require additional memory cost for registering and storing the input data, but also fail to dynamically compute and output the energy values in real time that causes a time delay. In other words, these methods can hardly meet the demands for rapid and accurate energy value detection.
In view of this, the present invention provides an energy detection apparatus and a method thereof which not only eliminates the additional memory cost and the time delay but also provides a real-time dynamic energy detection.